Electron beam line scanner with transverse binary control

ABSTRACT

A pair of dielectric plates have control electrodes formed on oppositely positioned broad surfaces thereof, there being an evacuated narrow space formed between such surfaces to provide paths for an electron beam between a cathode and a target. Such surfaces have conductive control electrodes formed thereon, the electrodes on one of the plates including paired electrodes arranged in a coded finger pattern defining electron beam channels between the cathode and target. The electrodes encompass substantially all of the plate surface area between which the channels are formed. Binary control signals are utilized to apply potentials to preselected ones of said electrodes to create transverse electric fields in the channels bounded thereby, thereby aborting the electron beam in such channels. The beam is in this manner permitted to pass through channels of the scanner in which there are no transverse fields so as to excite the target portions located by these channels.

United States Patent [451 0ct.3l, 1972 Honzik [54] ELECTRON BEAM LINESCANNER WITH TRANSVERSE BINARY CONTROL [72] Inventor: Richard A. Honzik,La Palma, Calif.

' [7 3] Assignee: Northrop Corporation, Beverly Hills, Calif.

[22] Filed: Aug. 31, 1970 [21] Appl. No.: 68,326

[52] US. Cl. ..315/10, 315/13, 313/83 [51] Int. Cl .1101] 31/26 [58]Field of Search ..315/10, 12, 13; 313/69, 76,

[56] References Cited UNITED STATES PATENTS 3,176,184 3/1965 Hopkins..315/13 R 3,331,985 7/1967 Hamann ..315/13 R 3,406,273 10/1968 Holland..313/76 X 3,408,532 10/1968 Hultberg et al ..315/12 3,483,422 12/1969Novotny ..315/12 3,539,719 11/1970 Requa et a1 ..315/13 R 3,560,9632/1971 Trilling ..313/76 3,600,627 8/1971 Goede ..315/13 R PrimaryExaminerCarl D. Quarforth Assistant Examiner-P. A. NelsonAttorney-Sokolski & Wohlgemuth and W. M. Graham [5 7] ABSTRACT A pair ofdielectric plates have control electrodes formed on oppositelypositioned broad surfaces thereof, there being an evacuated narrow spaceformed between such surfaces to provide paths for an electron beambetween a cathode and a target. Such surfaces have conductive controlelectrodes formed thereon, the electrodes on one of the plates includingpaired electrodes arranged in a coded finger pattern defining electronbeam channels between the cathode and target. The electrodes encompasssubstantially all of the plate surface area between which the channelsare formed. Binary control signals are utilized to apply potentials topreselected ones of said electrodes to create transverse electric fieldsin the channels bounded thereby, thereby aborting the electron beam insuch channels. The beam is in this manner permitted to pass throughchannels of the scanner in which there are no transverse fields so as toexcite the target portions located by these channels.

20 Claims, 6 Drawing Figures -u I PATENTED BT31 I972 3.701.922

SHEET 1 BF 2 FIG. 2

FIG. 3

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sum 2 or 2 FIG. 4

50 5| 52 53 55A ADDRESSING |B|As I BIAS I Hams Yams] CONTROL J 43[SWITCH [swnu k [SWITCHM [SWITCHIJ BEAM FIG'G INVENTOR RICHARD A. HONZIKQDKOLSKI 8| WOHLGEMUTH ATTORNEYS ELECTRON BEAM LINE SCANNER WITHTRANSVERSE BINARY CONTROL This invention relates to electron beam linescanners and more particularly to such a scanner utilizing a pair ofoppositely positioned plates which have coded electrodes thereon foreffecting the scanning of an electron beam between a cathode and atarget in response to a digital control signal.

In US. patent application Ser. No. 755,276, filed Aug. 26, i968, andassigned to Northrop Corporation, the assignee of the presentapplication, an electron beam line scanner with dynode plates havingthin conductive zigzag control strips thereon is described, in whichpotentials are applied between oppositely oriented strips to provide thescanning operation. In this device, a broad surface of each of theoppositely positioned control dynode plates is coated with a secondaryemissive resistive material. The thin conductive strips are arranged onthe plates over the secondary emissive material in a binary coded zigzagpattern, so as to define electron beam channels between the cathode andtarget. The plates are aligned with each other so that the zigzagpatterns of the strips of one plate are in phase opposition with thezigzag patterns of the other. Binary switching control circuitry isutilized to selectively provide potentials, transverse to the directionof the electron beam, between the oppositely positioned strip elementsin a manner such as to block the passage of electrons between thecathode and target in all but one selected electron beam channel at atime, the transverse electric fields effectively aborting the electronbeam in the channels where they are applied. The device of thisinvention, as in the device of the aforementioned application, utilizestransverse electric fields applied to coded conductive elements forcontrolling the beam of an electron beam line scanner. However, itdiffers from the prior device in that no secondary emissive or resistivesurfaces are required utilized. Rather, paired conductive controlelectrodes are utilized which encompass substantially all of the platearea between which the channels are formed. This greatly simplifies andlowers the cost of fabrication. Further, in the device of thisinvention, simple patterns which are relatively easy to form areutilized for the control electrodes for channeling the beam between thecathode and target.

The device of this invention has the advantage over the aforementioneddevice of easy alignment between the top and bottom plates in view ofthe fact that all of the coded information defining the channels may beon a single plate. Further, the need for having coded electrode patternson only one of the plates makes for greater simplicity and economy offabrication.

It is therefore the principal object of this invention to provide animproved electron beam line scanner utilizing transverse voltage controlwhich is simpler and more economical to fabricate than prior devices ofthis type.

Other objects of this invention will become apparent as the descriptionproceeds in connection with the accompanying drawings, of which:

FIG. 1 is a perspective view illustrating the general configuration ofone embodiment of the invention,

FIG. 2 is an exploded view illustrating the embodiment shown in FIG. 1,

FIG. 3 is a schematic drawing illustrating control circuitry for theembodiment of FIGS. 1 and 2,

FIG. 4 is a schematic drawing illustrating a noncoded control plate of asecond embodiment of the invention,

FIG. 5 is a schematic drawing illustrating control circuitry for theembodiment of FIG. 4, and

FIG. 6 is a perspective view of the control plates of a third embodimentof the invention.

Briefly described, the device of the invention comprises a pair ofnon-conductive plate members which are held with their broad surfacesopposite each other in close proximity so as to enable the formation ofa plurality of electron beam channels between a cathode and a targetwhich are positioned along opposite edges of the plate members. Meansare provided to establish and maintain a vacuum tight condition in thespace between the plate members. Means are further provided toaccelerate electrons from the cathode towards the target. Formed on thebroad surface of one of the plate members are a plurality of parallelrows of sets of paired electrodes, these electrodes being arranged in acoded finger pattern which defines a plurality of electron beam channelsrunning between the cathode and the target. The fingers of eachelectrode pair are interdigitated with each other. Non-coded electrodemeans is formed on the opposing surface of the other of the platemembers. The electrodes cover substantially all of the surface area ofthe plate members between which the channels are formed. Binary controlmeans are provided to selectively apply potentials to the electrodes ina manner such that there is a transverse electric field placed across aportion of the channels to be kept inactive, the channels with notransverse electric field thereacross being activated. In this manner,the beam can be directed to any desired portion of the target inresponse to the binary control signals.

Referring now to FIGS. 1 and 2, one embodiment of the invention isillustrated. Plate members 11 and 12, which are preferably of adielectric material such as glass or a suitable ceramic, are positionedwith their broad surfaces opposite each other, a narrow slot 14 beingformed between said surfaces. Plates 11 and 12 each have an end plate 17and 18 respectively attached thereto, these end plates extending beyondthe broad surfaces of their associated plate members so as to separatethe plates to form slot 14. In the assembled position, as shown in FIG.1, the edge portion 170 of plate 17 abuts against the surface of plate12 while the edge portion 18a of plate 18 abuts against the surface ofplate 11. End plates 17 and 18 are fabricated of a dielectric materialwhich may be similar to that of the control plates and may be attachedto the ends of the control plate by any suitable means such ascementing.

A cathode member 22 is positioned along one of the ends 11c and ofplates 11 and 12 respectively, in overlapping relationship so as toprovide a source of electrons along slot 14. The cathode member isseparated from the plates by insulator strips 26 and 27 placedtherebetween. Cathode 22 may be of the thermionic type or may be a coldcathode of the radioactive or field emission type. Positioned along theend portions 11a and 12a of the control plates is target member 21 whichis thus located opposite cathode 22 with the slot 14 located between thecontrol plates and extending between the cathode and target members. Thecontrol plate and target members are separated from each other by meansof insulator strips 28 and 29 located therebetween. Target 21 may becoated with a phosphorescent material capable of providing a luruinousdisplay with the impingement of electrons thereon or may be a memoryplate or the like for collecting or storing electrical charge inaccordance with the incidence of the electron beam thereon.

The assembled unit is maintained in a vacuum environment withinevacuated casing 25.

Control plate 12 has a single electrode 30 on the broad surface thereof.This electrode covers the entire surface of control plate 12 and may beof a highly conductive material such as gold, copper or aluminum whichmay be placed on the surface by suitable means such as vacuumdeposition. The end surfaces 12a and 120 are also preferably coveredwith conductive material. This plate may be entirely of a conductivematerial rather than comprising a dielectric substrate with a conductiveelectrode on a surface thereof.

Control plate 11 has a plurality of sets of coded electrodes 35a38a;35b38b thereon. These electrodes are of a highly conductive materialsuch as gold, copper, or aluminum. Electrodes 35a-38a; 35b-38b ofcontrol plate 11 as shown in FIG. 2 are arranged in a binary Gray code,electrodes 35a-38a each being paired in interdigitated relationship witha corresponding one of electrodes 35b-38b. Straight binary coding couldalso be utilized or other type of coding to an order other than binary.Each electrode is electrically insulated from each other electrode andis connected to appropriate switching circuitry as to be explained inconnection with FIG. 3. Also on the surface of plate 11 are acceleratorelectrode 44 and modulator electrode 42 These electrodes are of a highlyconductive material and are in the form of strips running along theopposite edges of the plate. Electrodes 42 and 44 preferably havecontiguous portions 420 and 440 which cover the plate end portions 11aand 110 respectively, this tending to minimize the possibility of chargebuild up in these areas which might adversely affect performance.

The integrated assembled unit thus comprises an electron emittingcathode 22 and an electron responsive target 21 between which aresandwiched a plurality of coded finger pattern electrodes forcontrolling the scanning of an electron beam between the cathode andtarget in response to digital control signals. The electron beam iseffectively aborted by placing a transverse potential between electrode30 and preselected ones of electrodes 35a-38a; 35b-38b, the electronbeam passing through to the target in the channels formed by the fingerpattern electrodes which have no transverse potentials thereacross.

Referring now to FIG. 3, the operation of the transverse controlutilized to implement the scanning operation is schematicallyillustrated. Power source 40 has its negative terminal connected tocathode 22 and its positive terminal connected to ground. Electrodes 30and 44 and each of switches 45-48 which may comprise suitable electronicswitching circuits such as flip-flops also are grounded. Power source 41is connected between ground and target 21 to provide a positivepotential on the target with respect to ground. Thus, an electric fieldis established accelerating electrons from cathode 22 towards target 21.Power source 40 establishes a relatively high potential between thecathode and the electrodes (in an operative embodiment of the order of1,000 volts). Connected respectively to each of switches 4548 is aseparate bias voltage source 50-53.

Each of the switches 4548 is selectively controlled in response tocontrol signals from addressing control 55. One of the outputs of eachof switches 4548 is connected to an associated one of electrodes 35a-38awhile the other output of each of the switches is connected to anassociated one of electrodes 35b-38b. The switching circuits maycomprise flip-flops which are arranged so that the conducting stagesthereof each feed through to their associated electrodes groundpotential while the non-conducting stages are simultaneously feeding thevoltage of appropriate ones of bias sources 50-53 to their associatedelectrodes. Thus, it can be seen that in response to addressing control55, potentials can be selectively established on each one of electrodes35a-38a, 35b-38b, to provide a potential difference between certain ofthese electrodes and electrode 30 and no potential difference betweenothers of these electrodes and electrode 30. The resulting electron beammay be intensity modulated by means of a modulation signal fed tomodulator electrode 42 from beam modulator 43.

For illustrative purposes, each of the outputs of switches 4548connected to electrodes 35b-38b are indicated by a plus sign in FIG. 3to provide a positive potential to each of these electrodes with respectto ground. A negative potential could be used as well. This potentialrepresents that supplied by each of voltage bias sources 50-53. At thesame time electrodes 35a-38a are receiving ground potential, the samepotential as that on electrode 30. Under such conditions, a transverseelectric field is created between electrode 30 and certain electrodes ofplate 1 l in all of the channels defined by the finger patternelectrodes except that to the far left. It is to be noted at this pointthat for the electrode pattern of plate 1 1 shown in FIG. 2, eightchannels are defined, these being delineated by each of theinterdigitated fingers of electrodes 38a and 38b. For the illustrativeexample, an electron beam as indicated by dotted line will pass from thecathode to the target, electron flow being aborted in all of the otherchannels by virtue of there being a transverse potential in some portionof each of these channels. It can readily be seen that by selectivelyactuating switches 4548 in various manners that the beam can be made topass through any of the channels to provide either a regular or randomscan. It is also to be noted that more than one of the channels can beenergized at a time such that plural beams are provided. Such type ofplural beam control requires separate independent switching control foreach of the electrodes of plate 1 l, to enable independent control ofthe potentials to the individual electrodes of each pair.

Electrodes 38a and 38b provide filtering action to minimize theappearance of ghost signals at the target. Such filtering is utilizedbecause it has been found that such ghosting may occur in channels wherethere is only a single electrode providing a transverse potential. Thefilter electrodes 38a and 38b are appropriately energized to assure thateach of the tumed off channels has at least two serially positioned electrodes therein for providing a transverse field, so as to insure thatthe channels to be de-activated are successfully cut off with nosignificant number of electrons passing through them to the target.

In an operative embodiment of the invention, the accelerating potentialprovided by power source 40 is on the order of 1,000 volts. Transverseswitching potentials on the order of only -15 volts are utilized whenthe electrodes of plate 11 have a width, w, which is 10 times theseparation 1 between electrode and the electrodes of plate 11. Theswitching potential requirements, it has been found, are a function ofthis width to separation ratio, the magnitude of the required switchingpotential varying inversely therewith.

While the embodiment of FIGS. 13 has been shown for only eight channels,it should be immediately apparent that the number of such channels canbe increased to any number desired by utilizing a greater number ofcontrol electrodes on plate 1 1 so as to define such additionalchannels.

It is to be noted that in the embodiment of FIGS. 1-3, the beamaccelerating potential is applied between the cathode and the controlelectrodes. These electrodes could therefore in certain embodimentsprocide the dual functions of beam acceleration and control,

' thereby permitting the elimination of accelerator electrode 44.

Referring now to FIGS. 4 and 5, one of the plate members and the controlcircuitry of a second embodiment of the invention is respectivelyillustrated. In this embodiment, a potential gradient is establishedbetween the cathode and target by segmenting the electrode means onplate 12 into a plurality of separate electrodes and applyingsuccessively higher potentials to these electrode segments and theoppositely positioned electrodes of plate 11. This potential gradientaids in accelerating the electron beam. Otherwise the remainingcomponents and operation are the same as for the first embodiment.

As can be seen in FIG. 4, plate 12 has a plurality of separateconductive electrodes 30a-30f thereon, these electrodes beingelectrically insulated from each other and, except for these insulatingseparation portions, covering substantially the entire surface of theplate. Electrodes 30b-30e are each positioned opposite an associatedpair of electrodes a, 35b-38a, 38b of plate 11. Electrodes 30a and 30frun opposite electrodes 44 and 42 respectively. Electrodes 30a and 30f,as for the embodiment shown in FIG. 2, also have contiguous portions(not shown) which cover the end portions 12a and 120 of the plate.

The potential gradient is established by means of voltage divider 65which is connected across power source 49. The positive temiinal ofpower source 49 is connected to ground, while the negative terminal isconnected to the acceleration electrodes 30a and 44. Taps 65b-65e ofvoltage divider 65 are connected to electrodes 30b-30e and switches -48respectively. Power source 41 is connected to target 21 to provide anelectron accelerating potential thereto. Thus, each one of theseelectrodes and the switch associated with the oppositely positionedelectrode on the other plate receives a potential which is increasinglyhigher as we go from the cathode to target. The switches 45-48 operateas in the first embodiment in response to addressing control 55 toalternatively connect to their associated electrodes either thepotential fed thereto from divider 65 or this potential plus (or minus)the bias potential supplied thereto from bias sources 5053.

As for the first embodiment, in the channels wherein oppositelypositioned electrodes have a potential difference establishedtherebetween so as to create a transverse electric field, the electronbeam is aborted, while in those channels where no such transverse fieldis created, the electron beam is permitted to pass through to thetarget.

The potential gradient between successive ones of electrodes 30a-30f maybe of the order of 25-50 volts where the other parameters aresubstantially the same as those indicated for the embodiment of FIGS.1-3.

Referring now to FIG. 6, the control plates of another embodiment of thedevice of the invention are illustrated. This embodiment differs fromthe previous embodiment in that grooves are provided in control plate 12to define electron beam channels. Otherwise, the device is similar tothe previous embodiments described. Control plate 12, which as for theprevious embodiments, may be of a dielectric material such as glass orsuitable ceramic, has a plurality of grooves formed in the broad surfacethereof opposite to the electroded surface of control plate 11. Thesegrooves are of a diameter such that they correspond and overlie each ofthe electron beam channels formed by the binary coded electrode patternon the opposite surface of control plate 11, this pattern being the sameas that shown in FIG. 2. Grooves 70 have electrodes 72 of a highlyconductive material such as gold, copper, or aluminum, depositedtherein. The electrodes 72 stop just short of the edges of the groovesso that there are insulating lands 74 formed between the grooves so asto avoid electrical contact between the electrodes of control plate 12and those of control plate 11. The control plates illustrated in FIG. 6are incorporated with the remaining structure and operated in responseto control signals in the same manner described in connection with theembodiment of FIGS. 1-3. v

It is to be noted that, if so desired, the grooved portions 70 canalternatively be formed in the surface of control plate 11 or in theopposing surfaces of both plates to form cylindrical channels. Theelectrodes 72 of control plate 12 are connected together so that theyall are maintained at the same potential by suitable interconnectionmeans (not shown). The utilization of grooved defined channels, asillustrated in FIG. 6, in certain instances tends to provide betterisolation between the individual channels, thus minimizing beam strayingfrom one channel to another.

It is to be noted, that it is possible to fabricate the device of theinvention with interdigitated coded finger pattern electrodesdistributed between plates 11 and 12 rather than having all of the codedelectrodes on one plate and all of the non-coded electrodes on theother. Distributing the electrodes in this fashion, however, makes itnecessary to accurately laterally align the plates with each other toproperly form the channels, which complicates the assembly of the deviceespecially where a great number of channels are involved.

This invention thus provides an improved line scanner utilizingtransverse control which is simpler and more economical to fabricatethan prior art devices, in which secondary emitting dynodes are nolonger required.

While the device of the invention has been described and illustrated indetail, it is clearly to be understood 'that this is intended by way ofillustration and example only and is not to be taken by way oflimitation, the scope and spirit of this invention being limited only bythe terms of the following claims.

I claim:

1. In an electron beam line scanner, an electron source, a target andmeans for accelerating the flow of electrons between said electronsource and target to form an electron beam therebetween, the improvementincluding means for causing said beam to scan said target in response toa digital addressing signal, comprismg:

a pair of plate members,

said plate members being positioned between the electron source andtarget with one of each of their broad surfaces opposite each other,said beam passing between said surfaces on a path substantially parallelthereto,

control electrode means on each of said opposite broad surfaces, saidelectrode means being positioned opposite each other,

said control electrode means comprising a plurality of sets of pairedelectrodes having finger portions arranged in a coded finger pattern todefine a plurality of electron channels running between the cathode andtarget, the finger pattern portions of the electrodes of each of saidsets of electrodes being interdigitated with each other, and noncodedelectrode means positioned opposite each of said sets of pairedelectrodes, and

means for applying potentials between pre-selected ones of said fingerpattern electrodes and said noncoded electrode means to providetransverse electric fields across selected ones of said channels,thereby preventing the flow of electrons in said selected channels, theelectron flow being permitted in those channels having no transverseelectric fields thereacross.

2. The scanner of claim 1 wherein said paired finger pattern electrodesare all arranged in successive rows on one of said plate members withthe non-coded electrode means being on the other of said plate membersopposite said paired electrodes.

3. The scanner of claim 1 wherein said paired coded finger patternelectrodes and said non-coded electrode means cover substantially all ofsurface area of the plate members between which said electron channelsare formed.

4. The scanner of claim 2 wherein said non-coded electrode meanscomprises a single electrode covering substantially all of the broadsurface area of the other of said plate members.

5. The scanner of claim 2 wherein said non-coded electrode meanscomprises a plurality of separate electrodes arranged in rows oppositesaid paired electrodes and means for applying successively higherpotentials to the opposite electrodes in going from the cathode to thetarget.

6. The scanner of Claim 1 wherein said means for accelerating the flowof electrons comprises an accelerator electrode positioned between saidcathode and said control electrode means and means for applying anaccelerating potential to said accelerator electrode.

7. The scanner of claim 1 and further including modulator electrodemeans interposed between said electron source and said target and meansfor supplying a signal to said modulator electrode means for modulatingsaid beam.

8. A electron beam line scanner comprising:

a pair of plate members,

control electrode means on one surface of each of said plate members,

means for positioning said plate members with the electrode means of onein opposing relationship and in close proximity to the electrode meansof the other,

the electrode means on one of said plate members comprising a pluralityof sets of paired electrodes having finger portions arranged in a codedfinger pattern to define a plurality of electron channels, the fingerpattern potions of each of said sets of electrodes being interdigitatedwith each other,

an electron source,

a target member,

said electron source and target members being positioned along oppositeedges of said plate members with said electrodes therebetween,

means for accelerating the flow of electrons between said electronsource and said target, the electrons passing between the surfaces ofsaid plate members, and

means ,for selectively applying a potential between preselected ones ofsaid paired electrodes on said one of said plate members and theopposing electrode means on the other of said plate members to provide atransverse electric field to prevent the flow of electrons between saidelectron source and said target in the channels encompassed thereby,whereby electrons flow to said target in the channels having notransverse electric field thereacross.

9. The scanner of claim 8 wherein the electrode means on the other ofsaid plate members comprises a single electrode covering substantiallythe entire broad surface thereof.

10. The scanner of claim 8 wherein the electrode means on the other ofsaid plate members comprises a plurality of separate electrodes arrangedin parallel rows opposite said paired electrodes, said acceleratingmeans comprising means for establishing a potential gradient runningfrom electrode to electrode between the cathode and target on both ofsaid plate members.

11. The scanner of claim 8 wherein the electrode means coverssubstantially all of the surface area of said plate members betweenwhich the channels are formed.

12. The scanner of claim 8 wherein said sets of paired electrodes arearranged in succession in substantially parallel rows.

13. The scanner of claim 1 wherein said channels are further defined bygrooves formed in the surface of at least one of said plate members.

14. The scanner of claim 13 wherein the grooves are formed in thesurface of the other of said plate members, the electrode means of theother of said plate members comprising conductive strips in saidgrooves.

15. The scanner of claim 8 wherein said means for accelerating the flowof electrons between said electron source and said target membercomprises an accelerating electrode positioned proximate to said sourceand means for providing a potential between said accelerating electrodeand said source.

16. The scanner of claim 8 wherein said positioning means is adapted toseparate the plate members from each other to form a narrow slot betweenthe surfaces thereof, the channels being formed in said slot.

17. An electron beam line scanner comprising:

a pair of plate members of a dielectric material,

an electron source,

a target,

control electrode means on one surface of each of said platemembers forcontrolling the electron flow between said electron source and saidtarget,

means for positioning said plate members with the electrode means of onein opposing relationship and in close proximity to the electrode meansof the other, electron paths between the electron source and targetbeing formed between said plate members,

the electrode means on one of said plate members comprising a pluralityof sets of paired electrodes having finger portions arranged in a codedfinger pattern to define a plurality of electron channels between theelectron source and target, the finger pattern portions of each of saidsets of electrodes being interdigitated with each other, said electrodesbeing arranged in successive rows,

the electrode means on the other of said plate members comprising asingle electrode covering substantially the entire surface thereof,-

s'aid electrodes covering substantially all of the surface areas of saidplate members between which the channels are formed,

said electron source and target members being positioned along oppositeedges of said plate members with said electrodes therebetween,

means for accelerating the flow of electrons between said electronsource and said target, the electrons flowing between said opposingelectrode means,

and

means for selectively applying a potential between preselected ones ofsaid paired electrodes on said one of said plate members and an opposingelectrode on the other of said plate members to provide a transverseelectric field to prevent the flow of electrons between said electronsource and said target in the channels encompassed thereby, wherebyelectrons flow to said target in the channels having no transverseelectric field thereacross.

18. The scanner of claim 17 wherein the means for accelerating the flowof electrons between said source and target comprises an acceleratorelectrode positioned on said one of said plate members between saidsource and said paired electrodes, and means for applying an electronaccelerating potential to said accelerator electrode.

19. The scanner of claim 18 and further including a modulator electrodepositioned on said one of said plate members and means for providing amodulation signal to said modulator electrode.

20. The scanner of claim 19 wherein said modulator and acceleratorelectrodes are positioned along opposite edges of said one of said platemembers, said modulator and accelerator electrodes extending over theopposite end portions of said plate member.

1. In an electron beam line scanner, an electron source, a target andmeans for accelerating the flow of electrons between said electronsource and target to form an electron beam therebetween, the improvementincluding means for causing said beam to scan said target in response toa digital addressing signal, comprising: a pair of plate members, saidplate members being positioned between the electron source and targetwith one of each of their broad surfaces opposite each other, said beampassing between said surfaces on a path substantially parallel thereto,control electrode means on each of said opposite broad surfaces, saidelectrode means being positioned opposite each other, said controlelectrode means comprising a plurality of sets of paired electrodeshaving finger portions arranged in a coded finger pattern to define aplurality of electron channels running between the cathode and targEt,the finger pattern portions of the electrodes of each of said sets ofelectrodes being interdigitated with each other, and non-coded electrodemeans positioned opposite each of said sets of paired electrodes, andmeans for applying potentials between pre-selected ones of said fingerpattern electrodes and said non-coded electrode means to providetransverse electric fields across selected ones of said channels,thereby preventing the flow of electrons in said selected channels, theelectron flow being permitted in those channels having no transverseelectric fields thereacross.
 2. The scanner of claim 1 wherein saidpaired finger pattern electrodes are all arranged in successive rows onone of said plate members with the non-coded electrode means being onthe other of said plate members opposite said paired electrodes.
 3. Thescanner of claim 1 wherein said paired coded finger pattern electrodesand said non-coded electrode means cover substantially all of surfacearea of the plate members between which said electron channels areformed.
 4. The scanner of claim 2 wherein said non-coded electrode meanscomprises a single electrode covering substantially all of the broadsurface area of the other of said plate members.
 5. The scanner of claim2 wherein said non-coded electrode means comprises a plurality ofseparate electrodes arranged in rows opposite said paired electrodes andmeans for applying successively higher potentials to the oppositeelectrodes in going from the cathode to the target.
 6. The scanner ofclaim 1 wherein said means for accelerating the flow of electronscomprises an accelerator electrode positioned between said cathode andsaid control electrode means and means for applying an acceleratingpotential to said accelerator electrode.
 7. The scanner of claim 1 andfurther including modulator electrode means interposed between saidelectron source and said target and means for supplying a signal to saidmodulator electrode means for modulating said beam.
 8. A electron beamline scanner comprising: a pair of plate members, control electrodemeans on one surface of each of said plate members, means forpositioning said plate members with the electrode means of one inopposing relationship and in close proximity to the electrode means ofthe other, the electrode means on one of said plate members comprising aplurality of sets of paired electrodes having finger portions arrangedin a coded finger pattern to define a plurality of electron channels,the finger pattern potions of each of said sets of electrodes beinginterdigitated with each other, an electron source, a target member,said electron source and target members being positioned along oppositeedges of said plate members with said electrodes therebetween, means foraccelerating the flow of electrons between said electron source and saidtarget, the electrons passing between the surfaces of said platemembers, and means for selectively applying a potential betweenpreselected ones of said paired electrodes on said one of said platemembers and the opposing electrode means on the other of said platemembers to provide a transverse electric field to prevent the flow ofelectrons between said electron source and said target in the channelsencompassed thereby, whereby electrons flow to said target in thechannels having no transverse electric field thereacross.
 9. The scannerof claim 8 wherein the electrode means on the other of said platemembers comprises a single electrode covering substantially the entirebroad surface thereof.
 10. The scanner of claim 8 wherein the electrodemeans on the other of said plate members comprises a plurality ofseparate electrodes arranged in parallel rows opposite said pairedelectrodes, said accelerating means comprising means for establishing apotential gradient running from electrode to electrode between thecathode and target on both of said plate members.
 11. The scanner ofclAim 8 wherein the electrode means covers substantially all of thesurface area of said plate members between which the channels areformed.
 12. The scanner of claim 8 wherein said sets of pairedelectrodes are arranged in succession in substantially parallel rows.13. The scanner of claim 1 wherein said channels are further defined bygrooves formed in the surface of at least one of said plate members. 14.The scanner of claim 13 wherein the grooves are formed in the surface ofthe other of said plate members, the electrode means of the other ofsaid plate members comprising conductive strips in said grooves.
 15. Thescanner of claim 8 wherein said means for accelerating the flow ofelectrons between said electron source and said target member comprisesan accelerating electrode positioned proximate to said source and meansfor providing a potential between said accelerating electrode and saidsource.
 16. The scanner of claim 8 wherein said positioning means isadapted to separate the plate members from each other to form a narrowslot between the surfaces thereof, the channels being formed in saidslot.
 17. An electron beam line scanner comprising: a pair of platemembers of a dielectric material, an electron source, a target, controlelectrode means on one surface of each of said plate members forcontrolling the electron flow between said electron source and saidtarget, means for positioning said plate members with the electrodemeans of one in opposing relationship and in close proximity to theelectrode means of the other, electron paths between the electron sourceand target being formed between said plate members, the electrode meanson one of said plate members comprising a plurality of sets of pairedelectrodes having finger portions arranged in a coded finger pattern todefine a plurality of electron channels between the electron source andtarget, the finger pattern portions of each of said sets of electrodesbeing interdigitated with each other, said electrodes being arranged insuccessive rows, the electrode means on the other of said plate memberscomprising a single electrode covering substantially the entire surfacethereof, said electrodes covering substantially all of the surface areasof said plate members between which the channels are formed, saidelectron source and target members being positioned along opposite edgesof said plate members with said electrodes therebetween, means foraccelerating the flow of electrons between said electron source and saidtarget, the electrons flowing between said opposing electrode means, andmeans for selectively applying a potential between preselected ones ofsaid paired electrodes on said one of said plate members and an opposingelectrode on the other of said plate members to provide a transverseelectric field to prevent the flow of electrons between said electronsource and said target in the channels encompassed thereby, wherebyelectrons flow to said target in the channels having no transverseelectric field thereacross.
 18. The scanner of claim 17 wherein themeans for accelerating the flow of electrons between said source andtarget comprises an accelerator electrode positioned on said one of saidplate members between said source and said paired electrodes, and meansfor applying an electron accelerating potential to said acceleratorelectrode.
 19. The scanner of claim 18 and further including a modulatorelectrode positioned on said one of said plate members and means forproviding a modulation signal to said modulator electrode.
 20. Thescanner of claim 19 wherein said modulator and accelerator electrodesare positioned along opposite edges of said one of said plate members,said modulator and accelerator electrodes extending over the oppositeend portions of said plate member.